Method for treating oils



Aug. 6, 1935. u. B. BRAY METHOD FOR TREATING OILS Filed. March 6, 1953 'INVENTOR.

Ulrzc 5 B ray BY A TTORNE Y.

means of solvents and low temperatures.

Patented Aug. 6, 1935 UNITED STATE The present invention relates PATENT OFFICE METHOD FOR TREATING OILS "Ulric B. Bray, Los Angeles, Calif., asslgnor to Union 011 Company of California, Los Angeles, CaliL, a corporation of California Application March 6, 1933, Serial No. 659,854

5 Claims. (01.196-13) to a method for separating asphalt from oil. More specifically, it relates to a method for'separating asphalt from asphaltic oils substantially fre invention is a continuation, in pending application Serial No. 6 9th, 1932.

e from wax by This part, of my co- 10,I30, filed May In the aforementioned co-pending application,

I disclosed a process for the co asphalt and wax by means of mally gaseous hydrocarbon solvent, in particular, liquid propane, wherein the asphalt and wax containing oil was commingled with der pressure suflicient to mainta -precipitation of a liquefied norsaid solvent unin the solvent in a. liquid state. This caused the asphalt to be thrown out of solution. Then a portion of the liquid propane was allowed to vaporize under reduced pressure to chill the mixture of oil, solvent,

wax and asphalt to a sufliciently low temperature to cause precipitation of the wax. The ebullition or boiling which accompanies the vaporization of the liquid propane caused a violent agitation of the mass and the precipitated asphalt acted as nuclear or gathering bodies for the agglomeration v of the wax as it was precipitated at the lower temperatures attained. The agglomerated particles of asphalt and wax were then separated from the oil solvent solution and the solvent was removed from the oil. This oil was a lubricating oil substantially free from asphalt and wax.

In the present discussion of my invention, by the term propane,I intend to include such hydrocarbons as are normally vaporous at ordinary temperature and pressure.

Such hydrocarbons include methane, ethane, propane, butane, iso-butane and mixtures thereof. These volatile solvents may be obtained by rectification of casing head gasoline by the so-called stabilizing method, n0w conventional in the natural gasoline industry. They are the overhead obtained. They are liquefied by compression and cooling in the conventional manner and are drawn ofi into pressure chambers where they are maintained in a liquid state until used. A typical analysis of such a fraction is 6.72% ethane, 19.91% iso-butane and 1.17%

72.20% propane, normal butane.

Such a fraction may be maintained in a liquid state at a pressure of 125 lbs.

per square inch at a temperature of about F. The predominating hydrocarbon member in propane and hereafter when I use the term "propane or liquid propane, I am a fraction. I In the foregoing process, I ha this mixture is referring to such ve observed that at lower temperatures.

the lubricating oilproduced is also substantially free from the heaviest viscous oilfractions and has a lower Conradson carbon value. It is my belief that the presence of these heavy viscous oil fractions in lubricating oils are largely responsible for the high Conradson carbon values ofthe oil. In the foregoing process of my copending application, the heaviest viscous oil fractions were removed by chilling the -oil containing both asphalt and wax. In other words, I have discovered that chilling an oil to precipitate wax will also effect precipitation of the heavy viscous oil fractions which, when separated from the oil, will produce a lubricating oil of lower Conradson carbon value.

' I have now discovered that substantially all asphaltic oils contain such heavy viscous oil fractions irrespective of whether they contain wax. It will be observed that all asphaltio oils contain more or less wax; some contain large quantitles of wax while others are substantially free but nevertheless contain a small quantity. Thus, such California crude oils as McKittrick, Poso Creek, Coalinga, Summerland and Sunset are typical asphaltic crudes containing very little wax, while other crudes as Montebello, Kettleman tions will not separate from the oil. My present invention is directed towards removal of such fractions from asphaltic oils substantially free from wax.

I have, therefore, discovered that on asphaltic oils substantially free from wax, temperature'influences the recovery and character of oil and asphalt separated from petroleum oils by means of solvents. At room temperatures, i. e. about F. and with the use .of equal volumetric ratios of liquid propane to residuum and on identical oil stocks, the percent of oil recovered will be greater and, therefore, the amount of asphalt will be. less than when the separation is carried out In other words, the reduction of temperature on the mixture of propane and residuum lowers the solubility of asphalt in recover a greater amount of asphalt at the lower temperature than at a more elevated temperature. Conversely, the yield of oil recovered becomes correspondingly lower with reduction of temperatures. However, the character of the oil produced is better, that is, it is clearer and has a lower Conradson carbon value. This may be attributed to the fact that the heavy viscous oil fractions normally present in the asphaltic oil which cause the increase of the Conradson carbon value of the oil are soluble in the solution of oil and propane at more elevated temperatures but are insoluble at lower temperatures and, therefore, are precipitated together with the asphalt whichthus lowers the yield of oil recovered.

It will be observed that by the term asphalt, I intend to include such fractions which will separate or precipitate from asphaltic oils substantially free from wax when such oils are commingled with liquid propane or other solvents. Thus, the mixture of heavy viscous oil fractions and the asphalt or bitumen content of the oil when separated therefrom by means of solvents at low temperatures will be considered an asphalt I have also discovered that I may obtain a greater yield of asphalt from asphaltic oils by using a, lower volumetric ratio of propane to residuum at the lower temperature than may be obtained by using higher volumetric ratios at more elevated temperatures. Thus, for example, on a Pose Creek residuum topped to an on-stream viscosity of 67 seconds Saybolt Universal at 100 F., I have recovered smaller quantities of oil and correspondingly greater amounts of asphalts byusing a volumetric ratio of 2.5 to l at a temperature of 20 F. than by employing a volumetric ratio of 5 to l. at 80 F. In the formercase, the

amount of oil recovered was about 74.5%, whereas when a volumetric ratio of 5 to 1 was employed at 80 F. the percent of oil recovered amounted to 79%. This amount may be lessened, that is, more asphalt may be precipitated from solution by increasing the volumetric ratio of propane to residuum. For example, by using volumetric ratios of 15 to -1 and 20 to 1, the percent of oil recovered will approximate 76.5% indicating that more asphalt is thrown out of solution. The oil recovered by using lower volumetric ratios and lowertemperatures had a better color and a lower .Conradson carbon value than any of the oils ex- In the above example, I commingled 4.2 parts of liquid propane to one part of Poso Creek residuum under pressure sufiicient to maintain the solvent liquid and then reduced the pressure to evaporate propane until approximately 2.5 parts of propane to one of residuum remained and the temperature was lowered to 20 F.

With the above discussion in mind, it will be perceived that it is an object of my invention to separate asphalt from an asphalt containing oil by means of a solvent at low temperatures, 1. e. approximately 0 to -;-40 F.

It is a further object to separate heavy viscous oil fractions from asphaltic oils substantially free 1 the propane oil solution so -that it is possible to from wax as well as the asphalt content of the oil.

Another object of my invention resides in commingling asphalt containing oil with a liquefied normally gaseous hydrocarbon solvent under pressure suificient to maintain the solvent liquid and then reducing the temperature of the mixture by releasing the pressure to evaporate a portion of the solvent and thus precipitate asphalt and heavy viscous oil fractions from the mixture, removing the precipitated asphalt and heavy viscous oil fractions under pressure from the oil solvent solution and separating the solvent from the oil.

Other objects and advantages of my invention will be apparent from the following description of my invention taken from the drawing which represents a schematic arrangement of apparatus for carrying out my invention:

Referring to the drawing, an asphalt containing oil substantially free from wax is taken from tank I and is passed into line 2 via pump 3 where it meets liquid propane taken from storage tank 4 via line 5 and pump 6 which forces the propane through valve i into line 2. The amount of propane introduced into line 2 will depend upon the character of the oil and the temperatures desired in decanter M. For example, operating on a Poso Creek residuum topped to an on-stream viscosity of 67 seconds Saybolt Universal at F., it is desirable to mix 4.2 parts of liquid propane to 1 part of the residuum so that in the subsequent vaporization of propane in decanter l0 approximately 2.5 parts of propane will remain and the temperature will be lowered to approximately 20 F. The mixture of liquid propane and residuum is passed through turbulence coil or mixing coil 8 andthen-through pressure reduction valve 9 into decanter or asphalt precipitator 50. In decanter l0 sufficient propane vaporizes to reduce the temperature of the remaining material to a sumciently low temperature which causes the asphalt and heavy viscous oil fractions to precipitate from solution. The de-.

sired low temperature is obtained by controlling the pressure in decanter MI by the proper operation of valve H on line 52 and compressor l 5 which is connected to the decanter by lines it and E2. The pressure to be maintained in the decanter ID will generally be about 0 to 25 lbs. gauge'which corresponds to a temperature of approximately between -40 F. to 0 F. As the propane solution passes through valve t, its pressure is reduced so that a portion of the propane evaporates in the decanter it and the vapors pass out of the top through line it controlled by valve H and then into line it to compressor l5 where the vapors are compressed, passed through line It, liquefied in cooler i i and passed to propane storage tank 4.

The asphalt precipitated in decanter I0 settles to the bottom of the decanter and is removed by line it controlled by valve 2| and pump 22 as a mixture of asphalt, heavy viscous oil fractions and propane. Pump 22 forces this mixture under pressure through heating coil 23 where it is heated to a sufilciently high temperature to melt the asphalt and vaporize the residual propane. The heated mixture is then flashed through pressure reduction valve 25 on line 24 into evaporator 29 which operates at a lower pressure. superheated steam is introduced into evaporator 29 through perforated pipe 3 to supply additional heat and to reduce the asphalt to the proper specification, generally only as regards flash and fire points. The overhead from evaporator 29 passing through mist extractor 3i vis sent through line 32 tov cooler 33 and then to separator 34. The uncondensed propane from separator 34 is sent through line 35 controlled by valve 36 to line 31 and line l4 to suction of compressor l5 where its pressure is a raised tothat in the high pressure system and is then sent to cooler H where it liquefies and runs down-into propane storage tank 4. Any condensed light oil in separator 34 is withdrawn through line 38 and condensed water through line 39. The asphalt is taken from the bottom of evaporator 29 and sent through line 40 con-'- trolled by v-alve 4| to storage tank 42.

The overflow from decanter Ill consisting of propane and oil free from asphalt and heavy viscous oil fractions and also wax is sent through line by pump 46 and then through line 48 controlled by valve 49 to acid treatment and neutralization with alkali, valve 5| on line 50 being closed. If desired, valve 49 on line 48 may. be closed and valve 5| opened so that the overflow from decanter I0 may pass into line 50 and then into evaporator or heater 52 provided with mist extractor 53 where the propane present isvaporized by the aid of steamcirculated through the closed steam coil 54. The vaporized propane passes out of the heater through line 55 controlled by valve 56 and then passes through cooler 51 into lines 58, 31 and I4 to compressor l5, cooler ll into storage tank 4. The propane-free oil passes from heater 52 by means of line 59 controlled by valve 60 into tank 5|. This oil will comprise a lubricating oil ,of low Conradson carbon content and free from heavy viscous oil fractions, wax and asphalt. The oil may be acid and alkali treated prior to its use or may be treated by other methods now conventional.

It is to be understood that the above is merely illustrative ofpreferred embodiments of my invention of which many variations maybe made liquefied normally gaseous hydrocarbon solvent to precipitate asphalt, reducing the temperature during said precipitation, congealing and precipitating heavy viscous oil fractions which are responsible for high Conradson carbon values of oils together with said asphalt, separating said precipitated heavy viscous oil fractions and asphalt from the oil solvent solution and separating residual solvent from the oil solvent solution to produce a. lubricating oil of low'Conradson carbon value.

pressure to vaporize a portion of the solvent to 4 thus chill the oil, congealing heavyviscous oil fractions which are responsible for high Conradson carbon values of oils in said oil, separat ing said precipitated asphalt and congealed heavy viscous oil fractions from the oil solvent solution and separating the residual solvent from the oil whereby a lubricating oil is produced having a low Conradson carbon value.

3. A method for separating asphalt from oil which comprises commingling an asphalt containing oil substantially free from wax with a liquefied normally gaseous hydrocarbon solvent and precipitating asphalt, chilling said mixture to a temperature between 0and -40 F. and congealing heavy viscous oil fractions which are responsible for high Conradson carbon values of oils in said oil, separating said precipitated asphalt and congealed heavy viscous oil fractions from the oil solvent solution and separating residual solvent from the oil.

4. A method for producing an asphalt containing heavy viscous oil fractions normally present in oils which comprises mixing an asphalt containing oil substantially free from wax with a liquefied normally gaseous hydrocarbon solvent and precipitating asphalt, chilling-said mixture and congealing and precipitating heavy viscous oil fractions which are responsible for high Conradson carbon values of oils, separating said congealed heaty viscous oil fractions and said precipitated asphalt from the oil solvent solution and separating the residual solvent from said separated congealed viscous oil fractions and asphalt.

5. A method as in claim 1 in which the liquefled normally gaseous hydrocarbon comprises propane.

ULRIC B. BRAY. 

